Methods and systems related to keyword searching processes. A list of keywords may be first represented by a set of short substrings. The substrings are selected such that an occurrence of a substring indicates a possible occurrence of one or more of the keywords. Input data may be initially pre-processed, so as to identify locations in the input data in which the substrings occur. Then, the identified locations are searched for occurrences of the actual keywords. The pre-processing scheme enables the keyword search process to search only in the identified locations of the substrings instead of over the entire input data.